The capillary reservoir technique was used to study the self-diffusion of 42K in LiBr-KBr melts (table 18). The activation energy for the tracer diffusion of 42K in eutectic mixtures, at temperatures ranging from 360 to 760C, was equal to 6.0kcal/mol.

Diffusion and Transport in Molten Alkali Halides. M.Chemla, P.Lantelme, O.P.Mehta: Journal de Chimie Physique et de Physicochimie Biologique, 1969, October, 136-43